1. Field of the Invention
The present invention relates generally to transit devices that include a slow protocol filter, and methods of transmitting information within a transit device between two high bit rate data links and a slow control link using a slow protocol filter. In particular, the present invention is directed towards transit devices and methods in which a first data link receives packets, and the slow protocol filter determines whether the packets are data packets or are slow protocol control packets, and the packets are forwarded to the second data link or to a slow protocol client, connected to the slow control link, depending on whether the packets are data packets or slow protocol control packets.
2. Description of Related Art
The advantages of network communication are increasingly evident. The convenience and efficiency of providing information, communication, or distributed computational power to individuals at their personal computers or other end user devices has led to rapid growth of such networks.
Today's network traffic often consists of secured transactions between financial institutions, distributed global corporations, research and defense installations. This requires high reliability links to be established over the network by means of a Slow Protocol control operating between end stations and intermediate stations that can quickly diagnose link failure and administer corrective actions.
Most network communication is accomplished with the aid of a layered software architecture for moving information among host computers connected to the network. The layers help to create a task hierarchy, and the general functions of each layer is often based on an international standard called the Open Systems Interconnection (“OSI”). OSI sets forth seven processing layers through which information may pass when received by a host, in order to be presentable to an end user. Similarly, information from a host to the network may pass through those seven processing layers in reverse order. Another reference model that is widely implemented, called transport control protocol/internet protocol (“TCP/IP”), essentially employs five of the seven layers of OSI.
At the Physical level networks may include, for instance, a high-speed bus such as an Ethernet connection or an Internet connection between disparate local area networks (“LANs”), each of which includes multiple hosts, or any of a variety of other known means for data transfers among hosts. According to the OSI standard, physical layers are connected to the network at respective hosts, with the physical layers providing transmission and receipt of raw data bits via the network. The rules governing each layer are collectively termed as the “protocol” of that layer. In networking, Media Access Control (“MAC”) constitutes the Data Link Layer or Layer 2 of the OSI model.
As network needs grow progressively complex some of the layers such as the MAC layer are getting further refined to include sub-layers to cater to the high availability and high reliability demands on the link. One such sub-layer “Operation Administration and Maintenance (OAM)” in order to control various aspects of operation of terminal devices at the Data Link layer defines a class of control protocols known as “slow protocols” supportable by software implementing the protocol on a microprocessor and have minimal impact on bandwidth consumed provided the slow protocol frames can be identified and forwarded to the microprocessor. However, no such mechanism has yet been defined for intermediate transit devices.